1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus, and more particularly, in an apparatus in which media for recording information rotate, to a latch mechanism that is capable of holding and releasing a mechanism that is inside this apparatus.
2. Description of the Related Art
Mechanisms that employ wind power, which is generated by the rotation of media for recording information, for the holding and releasing of a head for reading and writing information on these media, are disclosed, for example, in U.S. Pat. Nos. 5,319,511, 4,538,193, and 4,692,829, and so forth. However, while a member for taking up wind that is on given media is disposed in the inventions of these publications, no consideration is given to the use of shock-resistant surfaces in an information recording apparatus.
The latch mechanisms of U.S. Pat. No. 5,319,511, and so forth, have a fin that is disposed so as to extend to the top of such media and at the gap between one medium and another medium. Wind, which is produced when the media rotate upon startup of the apparatus, is received by this fin, thus causing rotation of the latch mechanism, whereby a carriage of the apparatus is released from a restrained state. When the apparatus is stopped, magnetic members, which are provided on a latch of the latch mechanism, are attracted by magnetic flux leaking from a voice coil motor (hereinbelow, termed VCM where appropriate). When the apparatus is started up, the latch mechanism is caused to rotate in the reverse direction, whereby the carriage is restrained. The rotational center of the latch mechanism is constituted by mating a hole-shaped rotational center, which is in a latch molded from a resin, with a pin that is press-fit into a base, and by pushing this rotational center onto this pin.
Here, when the latch mechanism is in a position at which the carriage is released from a restrained state, if the attraction force causing action by the magnetic members of the latch with respect to a VCM magnet is not strong enough to counter the friction force at the rotational center of the latch mechanism, the latch is unable to rotate to return to an original position thereof at which the carriage was restrained.
According to these known examples, magnetic members are disposed in one location. With magnetic members in one location, in order to maintain an attraction force that exceeds the friction force at the rotational center of the latch when the latch is in a position that is farthest from the magnet, a strong attraction force is concentrated on magnetic members in one location. Consequently, the combined force resulting from the attraction force within the range of rotation of the latch, and the friction force, is not constant, and hence the difference between a minimum value and maximum value for this resultant force is considerable.
In such a latch mechanism, it is ideal for magnetic members, which are provided on a latch, to receive a magnetic force (attraction force) from the VCM only in the direction of rotation of the latch, this being the drive direction. Here, efficiency is extremely good. However, the present inventors have discovered that, since, in actuality, a magnetic force also acts in a direction perpendicular to the rotation of the latch, a problem exists of considerable friction at the rotational center of the latch.
In addition, in order to obtain a wind power that counters the force from the VCM that acts on the magnetic members, particularly in an apparatus that has one medium or two media and is relatively small, in order to maintain an attraction force, however small, wind power must be received by a fin being disposed so as to extend to the top of the medium/media. Further, with regard to the positioning of the fin such media are covered by same, it is unfavorable for there to be a risk of the media and the fin colliding with one another, or of the surface of the media being damaged, when the apparatus is subjected to shocks from the outside.
By means of this constitution, when the attraction force is strong, there is a requirement for the wind power to also be strong, and the present inventors have discovered that there is a problem of wear to the components at the rotational center, resulting from same being caused to rotate in a strong dynamically balanced relationship, and of the life of these components being short. The present inventors have discovered that, on account of the fact that the cross-sectional shape of the latch mechanism must be made large due to the requirement for the components to be strong enough to endure a strong dynamically balanced relationship, a problem arises of high material costs. The present inventors have also discovered that, as a result of making the cross-section of the latch broad, the latch as a whole becomes heavy, and the imbalance of the latch is such that the ability of the apparatus to withstand shocks is reduced (there is a tendency for the latch to move as a result of these shocks). Also, as a consequence of obtaining a strong wind power with respect to a strong attraction force, a fin, which extends to the top of the media, induces turbulence in the flow of air on the surface of the media, whereby the stability of the head against upward floatation thereof is adversely affected. A further problem has been discovered in that, as a result of the problem of vibrations of the magnetic recording media, which are caused by this turbulent flow, it is not possible to make such media thin.
In addition, when the latch mechanism is being disposed in the apparatus, since the criterion for positioning the latch components is to place same on a base, and also because the magnetic members are disposed at one location, the present inventors have found that a problem arises in that there is a potential for a considerable positional error between the magnetic members and magnet, and in that the timing for movement of the latch is irregular. In the prior art, there has been a requirement for strict precision for components between the magnet and magnetic members. It has, however, been discovered that this requirement cannot be reconciled with a demand for miniaturization of the apparatus or for a constitution thereof with high component density.
Furthermore, from the viewpoint of shock resistance, the disposition of any member whatever on the media for recording information, for example of a head supported by an actuator, is by no means favorable. Consequently, when an actuator is held under the action of a latch mechanism, the present inventors have considered the fact that a head, which is supported by an actuator, or any components accompanying this head, must not be present on the media for recording information.
Further, US Patent publications such as U.S. Pat. No. 4,538,193, disclose a mechanism that performs release of the carriage by releasing a latch, by causing same to rotate, under the action of wind power in the space between the surface of a medium, which is closest to the base, and the base; and that restrains the carriage by causing the latch to rotate in the opposite direction by means of a spring. In U.S. Pat. No. 4,692,892, release of the carriage is performed in the same manner, but the carriage is restrained by means of a mechanism that causes the latch and base to rotate in opposite directions to one another as result of repelling action by a magnet provided on the latch and base, respectively. The same problems are posed by these patent publications and by U.S. Pat. No. 5,319,511.
In an apparatus of the prior art, a magnetic member is disposed in one location. With the magnetic member in one location, therefore, in order to attempt to maintain an attraction force that exceeds the friction force at the rotational center of the latch when the latch is in a position that is farthest from the magnet, a large force is concentrated on the magnetic member that is in one location. Consequently, the disparity between the minimum value and maximum value of the attraction force of the magnet is considerable within the range within which the latch rotates, and this has produced a variety of problems.
By disposing magnetic members in a plurality of disperse locations, in the latch mechanism, it becomes possible to attenuate the fluctuations in the attraction force generated by the magnet. Magnetic force that does not contribute to the movement of the latch mechanism should be also reduced. The latch mechanism is constituted such that the fin, which serves to take up the wind power, is not shifted over the recording surfaces of the information recording media, and such that the fin is not placed on the surfaces of the recording media.
More specifically, magnetic members are disposed in two separate locations, these two separate magnetic members being arranged in the vicinity of the VCM magnet such that the combined force resulting from the magnetic force, which is within the range of rotation of the latch and is caused by the magnetic flux leaking from the VCM, and from the friction force of the latch, becomes even.
Further, xe2x80x9clatch mechanismxe2x80x9d is intended to refer to a mechanism that comprises, as components, a latch, and peripheral components or parts of the apparatus that are employed in conjunction with this latch.